Fuel injection diesel engines are widely employed in the trucking industry. It is known that such engines operate most efficiently when the coolant temperature is controlled. Thus, it is customary to have a thermostatically-controlled cooling system associated with such engines. It has also been the practice to utilize fuel pumps which in effect pump an excess of diesel fuel to the engine and are provided with means to divert back to the fuel tanks such excess fuel as is not required to operate the engine at the particular time the fuel is being pumped. Typically, the fuel which is pumped to the engine reaches the engine at ambient temperature.
It has been previously recognized that diesel engine efficiency and, thus, miles obtained per gallon of diesel fuel consumed have some relation to the temperature of the diesel fuel at the time it reaches the fuel injection system associated with the diesel engine. Suggestions have been made in the prior art literature that the engine coolant as well as the exhaust gas apparatus could be used as a source of heat for heating the diesel fuel prior to injection. However, so far as is known, until the introduction of applicant's copending application apparatus, the trucking industry had never been provided with a practical auxiliary apparatus which would be incorporated into the fuel supply system of the truck engine and use the engine coolant as a source of heat to increase the fuel efficiency. Thus, the general object of the invention is to increase the fuel efficiency, i.e., the miles obtained per gallon of diesel fuel consumed, of a fuel injection diesel engine such as widely employed in tractor-trailer rigs. A more specific object is to improve upon the apparatus of copending application Ser. No. 097,329. Other objects will appear as the description proceeds.